The invention is based on a fuel injection pump for internal combustion engines. In a fuel pump of this type known from German Offenlegungsschrift DE-OS 39 43 419; U.S. Pat. No. 5,102,047 a pump piston is axially guided in a cylinder bore of a pump housing and is driven back and forth by a cam drive. With its face end remote from the cam drive, the pump piston defines a pump work chamber in the cylinder bore into which a fuel line discharges and which communicates with an injection valve, which protrudes into the combustion chamber of the engine to be supplied, via a pressure line. The onset of high pressure delivery of the fuel in the pump work chamber and consequently the onset of injection as well as the quantity of fuel to be injected is electrically controlled by means of the closing time of a magnet valve disposed in the fuel line, dependent upon the operating parameters of the engine to be supplied.
The transfer of the driving motion of the cam drive to the pump piston takes place via a tappet bolt, which acts upon the pump piston via a tappet insert. The tappet insert is disposed in a guide bush, which slides into a housing-mounted guide tube and which transfers the restoring force of a spring to the pump piston, which is fixed between the guide bush and the tappet insert via a coupling part.
Guiding and securing the end of the tappet bolt facing the pump piston is relatively expensive, since the axial securing of the tappet bolt in the tappet insert in the known unit fuel injector is achieved via a securing ring that is locked in the tappet and is fixed in an axial position between the face end of the tappet insert and an intermediate bush; the intermediate bush, for its part, is held axially on the tappet bolt via a snap ring in the bore of the guide bush into which the tappet bolt is guided.
This costly axial securing of the tappet bolt in the tappet insert makes manufacture and installation expensive. Furthermore, because in the operating state of the pump, this connection between the tappet bolt and the pump piston is nondetachable, this inevitably leads to the malfunction of the cam drive in the event of a jammed piston, i.e. blocking of the pump piston.